It has already happened that many different microorganisms and bacteria live on our planet.
Some species of them also live in the human body, coexisting peacefully with it and without causing any health problems.
But there are also those that, when they enter our body, behave extremely aggressively, causing disruption of organ function, the appearance of diseases and other negative consequences.
Thus, there are parasites from the genus opisthorchiasis, the presence of which in the body results in the appearance of a severe disease consonant with their name - opisthorchiasis.
At the moment, scientists know the only way the larvae of this type of parasite enter the human body is through the consumption of infected fish.
In the article we will figure out which fish should be consumed with special care, how to understand that it is not infected with opisthorchid parasites, and how to properly process fish before eating in order to avoid the possibility of infecting the body.
What does opisthorchiasis look like in fish?
River fish feed on shellfish. If the prey is infected with opisthorchid eggs, then after they penetrate the stomach, the parasites leave their primary host and settle in the vessels and muscle tissues of the second. Then they turn into a metacercaria - an oval cyst, inside which an arched larva lives.
To the question whether and how it is possible to determine whether fish are infected with helminths, there is one answer - opisthorchid larvae are invisible to humans. They can only be examined by a specialist using a microscope.
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Read further:
What can you become infected with opisthorchiasis when consumed? Dangerous foods
Developmental cycle of the liver fluke, intermediate host
How to treat fish for opisthorchiasis in order to kill parasites 100% and not become infected
Opisthorchiasis in cats: symptoms, drugs for treatment, can you get infected from a cat?
What worms can you get from a cat: a list of common cat worms
Can there be worms in chicken eggs: how to determine this and whether they can be consumed
What fish has opisthorchiasis: list of species
There is a claim that opisthorchiasis lives in river fish of a non-predatory breed. The content of concentrated cholic acid in the body of river predators (contained in bile) really does not allow helminths to live in them. However, sometimes a predatory fish that eats an infected fry becomes a carrier of a parasitic infection.
Pike
The question of whether pike suffers from opisthorchiasis worries people who value its white meat for its beneficial qualities. We are talking about a predator fish, which means that due to the high content of cholic acid, parasite larvae cannot live in its body. In rare cases, opisthorchiasis is found in pike. This happens to fish that live in very polluted water bodies.
Perch
Perch is a river predator. Living in a pond polluted by sewage, feeding on fry infected with helminths, it can also become a carrier of infection.
It is important to thoroughly wash your hands, dishes, and cutting board after handling river fish products.
Opisthorchiasis survives in fish also because the environment or weather conditions sometimes negatively affect the immunity of river inhabitants.
Peled
Knowing from which fish you can become infected with opisthorchiasis, there is a chance to prevent the penetration of worms into the body. Peled belongs to the salmon family. It is believed that this breed is resistant to parasites of the opisthorchid genus.
Rudd
This type of river animals is considered a potential carrier of opisthorchiasis larvae. Rudd is bony, so it is usually consumed dried and dried (that is, without heat treatment), which contributes to human infection with helminths.
Sterlet
The body of fish from the sturgeon family is resistant to liver flukes. This product comes to the sales counter mainly from fish factories, so the factor of infection of products with other types of helminths is minimal.
Ide
It lives in fresh water bodies and belongs to the carp family. May be a carrier of liver parasites.
Muksun
In fish of the salmon family, the likelihood of infection with opisthorchiasis is low. Infection of muksun can occur during the spawning period, when the school enters the lower reaches of the river. Muksun is sold in the form of lightly salted balyk and thin frozen slices, which contributes to human infection with parasites.
Zander
Opisthorchiasis in pike perch is unlikely. Pike perch is a predator; it is considered the most trouble-free river animal.
Other types
Knowing which fish suffers from opisthorchiasis, it should be subjected to more thorough heat treatment. Potential carriers of liver fluke larvae are:
- crucian carp;
- bream;
- ram;
- roach.
Where can you get infected?
Animals and humans are susceptible to opisthorchiasis. The causative agent of the disease is the cat fluke, which belongs to the class of liver flukes. With the feces of the sick person, the eggs of the parasite end up in a body of water, where they are eaten by snails. In their body they go through an intermediate stage of development, and then the fish become infected. A person can get sick after consuming a river product that has not undergone the required heat treatment.
You can avoid infection if you know where the infection is spread. The disease develops in river inhabitants and is widespread in the European part of Russia. Favorable conditions for the development of larvae are bodies of water with standing water or slow flow.
Take a test for opisthorchiasis
Infection found in:
It is especially dangerous to eat inhabitants of reservoirs with sewage. As a rule, fishing in such areas should be carried out with caution or be prohibited altogether.
The highest infection rates are believed to be in Thailand, Vietnam and Laos. Therefore, when visiting these countries, it is advisable to avoid eating fish products.
How to properly process fish
Opisthorchiasis fish is treated with cold and heat. A concentrated solution of table salt helps rid river fish meat of worms.
Freezing
When freezing fish, opisthorchid larvae die only at –10°C, but this is provided that the product is stored in the freezer for a week. To rid carcasses of the liver fluke within three days, it is necessary to reduce the temperature to –25°C.
Heat treatment
When asked at what temperature opisthorchids die in fish, experts answer that fluke (liver fluke) larvae do not die at a temperature of +40°C. They need heat treatment at a higher temperature - boiling, smoking, cooking or baking at 100°C.
Pickling
The most unreliable way to get rid of worms from a product. The question of how much salt fish needs to be salted to kill opisthorchiasis should be given careful attention. Inside small fish (less than 25 cm long), the larvae can survive even after two weeks of salting. Therefore, large carcasses must be kept in a salt solution for more than 30 days. The brine is prepared at the rate of 270 g of salt per 1 kg of fish.
Drying
When dried, fish meat is no less dangerous to health than after salting. Therefore the treatment should last about 3 weeks.
How to kill opisthorchiasis by drying:
- The fish are left in salt for 2-3 days; the salting period depends on the size and weight of the carcasses. Use 12-14% salt by weight of the carcass.
- Fish carcasses are dried for 2-3 weeks.
Other methods
Additional methods for disinfecting fish from larvae:
- Worm larvae settle not only in the caviar and liver, but also on the back and belly under the fins, in the gills, and in the eye sockets of the fish, so when cutting its head and fins it is better to immediately cut it out.
- Fish pieces should be fried by pouring plenty of vegetable oil, covering with a lid, making a cut along the ridge.
- It is recommended to steam fish in portions, approximately 150 g each.
- Pies with fish filling should be baked for about 30 minutes.
Historical excursion
The Italian scientist S. Rivolta first encountered this parasite, who discovered it in the liver of an dissected cat (1884), but was unable to determine the species of the helminth. In 1885, the Englishman R. Blanchard compiled the correct description of the helminth and called it the cat fluke. The disease itself caused by this parasite is called opisthorchiasis. Later, 6 years later, Professor K.N. Vinogradov (Tomsk University), while examining the corpse of a 34-year-old man, discovered unknown flat and white worms in the patient’s liver, the size of which did not exceed 1.5 cm, described them in detail and named them the Siberian fluke. As it turned out later, we were talking about a similar parasite.
In 1893, scientist Brown suggested that the disease occurs in those living on the shores of fresh water bodies, which was confirmed experimentally by researcher Askanazi (1904) - people who eat freshwater fish that have not undergone proper culinary processing get sick.
Is opisthorchiasis dangerous for humans?
After penetrating the human body, opisthorchid larvae settle in the liver and bile ducts. Then they become sexually mature and reproduce. Their parasitism in the hepatobiliary system (liver, gall bladder) leads to the appearance of an itchy rash. An infected person suffers from discomfort in the right hypochondrium and constantly feels sick.
If the worms block the bile ducts, the patient's skin turns yellow. If left untreated, the liver worm can destroy liver cells, provoke the appearance of a malignant neoplasm, and disrupt the functioning of the cardiovascular system.
The causative agent of the disease
Some fish are carriers of opisthorchiasis. This type of parasite belongs to flatworms, or more precisely, to digenetic flukes. The final carriers are mammals that feed on fish, as well as humans. An adult individual has a flattened body, 0.8-1.4 cm long, equipped with two suction cups that fix it in the host’s body.
In humans, parasites live in the following places:
- hepatic ducts;
- biliary tract;
- gallbladder;
- pancreas;
- pancreatic ducts.
Nutrients are obtained using suction cups, sucking them out of the tissues to which they are attached. These flukes are equipped with two pairs of reproductive organs (hermaphrodites). An adult can lay up to 800-900 eggs per day.
Opisthorchiasis
Geographical distribution and statistics
The largest focus of opisthorchiasis in the world is Russia - Tyumen region (Yamalo-Nenets and Khanty-Mansiysk districts), Altai Republic, Tomsk and Omsk regions, Novosibirsk region. The disease is also common in some areas of Ukraine and in Kazakhstan and Southeast Asia (the countries of Thailand, Cambodia, Vietnam, Laos). Occasional cases of opisthorchiasis have been reported in North America and Europe.
In Ukraine and the Russian Federation, the basins of the following rivers (quiet flow and abundance of shellfish) are endemic areas for this disease:
- Dnieper;
- Yenisei;
- Seversky Donets;
- Southern Bug;
- Don;
- Kama;
- Gum;
- Vorskla;
- Volga;
- Ural;
- Northern Dvina;
- Ob;
- Biryusa;
- Irtysh and others.
Most often, males aged 15–50 years are affected.
Statistics
- The number of people infected with opisthorchiasis around the globe is 21 million, two thirds of whom live in Russia.
- The level of infection with this parasite reaches 100% among the indigenous inhabitants of the North due to local traditions (raw food diet: stroganina, lightly salted fish).
- Every year 40,000 cases of the disease are registered in Russia.
- In the Russian Federation, up to 75% of residents suffer from opisthorchiasis.
- In Belarus, 3–5% of the population is infected with the parasite.
- In Ukraine and Kazakhstan, the percentage of patients with this disease reaches 7–10.
- In the Baltic countries, the infection rate of the population is 4–5%.
Doctor's recommendations
A person who is sick must follow a certain diet, which involves a complete abstinence from smoked, fatty and sweet foods, as well as eggs and tomatoes. To prevent intoxication, you should drink a lot of water. You should also pay attention to the temperature of the food and the method of eating it - in small portions six times a day. All foods must be baked or boiled.
The duration of the carbohydrate diet is 50 days and its main goal is to normalize the functioning of internal organs, the immune system, as well as cleanse the body of all parasites.
It is important to include in your diet foods that normalize the flow of bile. Crumbly cereals are most suitable for this. Soups form the basis of treatment. Vegetable and dairy products are most suitable.
Prohibited products include:
- preserved and smoked products;
- soups based on meat, mushrooms and fish;
- chocolate, cocoa and ice cream;
- fresh bread;
- boiled and fried eggs.
